DESIGN OF UH-1 CMRB TO MINIMIZE HELICOPTER VIBRATION

A composite main rotor blade (CMRB) was designed and flight-tested on an Army UH-1 helicopter. The CMRB was designed to be interchangeable in sets with the existing metal blades and to be superior in performance. To achieve the interchangeability, the CMRB was to be compatible with the existing hub, autorotation characteristics, control system dynamics, and aircraft vibration levels. In this paper, a brief description of the metal blade is made and dynamic analyses of the CMRB are presented. The effects of blade built-in twist, chordwise cg, blade pitching moment coefficient, live twist, and blade planform on cockpit vibrations and rotor system loads are discussed. An analytical explanation is provided as to why the prototype CMRB produced high cockpit vibrations and how a production configuration of the CMRB was achieved. Correlations of analytical predictions and flight test data are presented. A brief summary of the aerodynamic performance and dynamic compatibility of the CMRB with the metal blade is also provided.